Osprey makes good packs. I would get a 50-60L that should be plenty for a multiday trip if you go fairly light and don't want to bring a kitchen sink.
As far as boots, depends on the type of terrain you'll be covering and the conditions. Anything well traveled and relatively mild approach, a decent pair of approach shoes will do just fine. With a heavy pack however and changing terrain a decent pair of boots with ankle support are definitely a big plus. La Sportiva, Lowa, Scarpa all make good GTX type boots.
As far as gear...there is so much and it never ends.